docs: def write_credentials(self, credentials=None, profile=None,
                            cache_token=None):
          """Write credentials.
  
          Write credentials to credentials file. Performs ``upsert``.
  
          Args:
              cache_token (bool): If ``True``, stores ``access_token`` in token store. Defaults to ``True``.
              credentials (class): Read-only credentials.
              profile (str): Credentials profile. Defaults to ``'default'``.
  
          Returns:
              int: Affected document ID.
  
          """
          d = {
              'profile': profile,
              'client_id': credentials.client_id,
              'client_secret': credentials.client_secret,
              'refresh_token': credentials.refresh_token
          }
          if cache_token:
              d.update({'access_token': credentials.access_token})
          with self.lock:
              return self.db.upsert(
                  d, self.query.profile == profile
              )